Key result
Two-capacitor biphasic waveforms show equivalent defibrillation energy requirements to single-capacitor waveforms.
Why the study?
The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may enable simpler, smaller internal defibrillator designs, but the optimal capacitor combination was unknown.
Optimal dual-capacitor biphasic waveforms may enable simpler ICDs; leaves open clinical translation.
INTRODUCTION: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. METHODS AND RESULTS: Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 microF) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 microF, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23+/-2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of < or =40 microF had the same E50 (6.7+/-1.7 J to 7.3+/-3.9 J) as the single-capacitor truncated waveform (7.3+/-3.7 J), whereas waveforms with phase-2 capacitors of > or =60 microF had an extremely high E50 (14.5+/-10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of > or =60 microF additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344+/-65 V to 407+/-50 V vs 339+/-83 V). CONCLUSION: Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors.
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Fishler et al. (2000) studied Ventricular fibrillation (n=12). Full-discharge two-capacitor biphasic waveforms vs. Single-capacitor truncated waveform (120 microF, 65/65% tilt) was evaluated on E50 (energy required for 50% defibrillation success). Full-discharge two-capacitor biphasic waveforms with phase-2 capacitors ≤40 µF achieved equivalent defibrillation energy requirements (6.7-7.3 J) compared to a single-capacitor waveform (7.3 J).
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